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Andrew J Coia, Steven K Shevell; Perceptual Resolution with Simultaneous Ambiguous Color and Form. Journal of Vision 2019;19(10):89. doi: https://doi.org/10.1167/19.10.89.
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Color and form are features that can link separate regions of the visual field, but how do multiple linking features interact? One possibility is that common color and form enhance grouping of separate regions more than either feature alone. An alternative is that grouping is mediated by only one feature at a time. This study separates the perceptual grouping from color and from form when both features are ambiguous. METHODS: Two separate equiluminant patterns were presented above and below fixation in chromatic interocular switch rivalry (Christiansen, D’Antona, and Shevell, 2017). The dichoptic patterns rivaled in chromaticity (appearing red or green) and spatial frequency (2 or 5 cpd) with the dichoptic gratings always presented orthogonally. In some conditions, both features within the two separate patterns were the same (e.g. both 2 cpd/green); in other conditions, chromaticity and form were mismatched between the two rivalrous patterns. In separate trials, observers held buttons when (a) both patterns appeared the same color or (b) both appeared the same form. Independence predictions for the two patterns were derived by measuring percepts for each dichoptic pattern presented alone. RESULTS: While all observers showed perceptual grouping of the regions when stimuli had both features in common, grouping was less consistent though still found with a single feature in common. In these trials, observers fell along a continuum, with some showing a bias toward grouping by color, others a bias towards grouping by form, and others showing no significant bias. CONCLUSION: Having both chromaticity and form in common enhance grouping only compared to when the weaker of the two features alone was in common. The magnitude of grouping for two common features is limited by the strength of grouping for the stronger feature, in contrast to the general principle that an additional common feature enhances grouping.
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